Dexter's Fortress Oil Cap provides revolutionary protection for your trailer axle. Engineered with precision, Fortress includes a durable Dexter genuine bolt-on and threaded bearing protection solution. Its reinforced retainer ring design offers a shielded clear viewing lens, safeguarding against damage. Built from cast aluminum and enhanced with a resilient black coating, the cap provides an additional layer of robust protection. A resilient rubber O-ring and gasket ensure airtight sealing for optimal performance.